Electronic reading aid for the blind



Dec, 2-1, 1948. v. K. ZWORYKIN ET AL 2,457,099

ELECTRONIC READING AID FOR THE BLIND Filed June 8, "1946 /VOL gray?@Ja/z Mme. cam/ferie z'y. il

- I 'INVENToR' 'I//adgm/'K Z100/Wm feffze E, Fla/y N M Patented Dec. 21,1948 U N I TED .S TATES PAT- ENT OF FI CE ELECTRONIC READING;`AIDFOR'"FREI-BLIND Vladimir K. Zworykin and LesliefE. Elory,-Princeton, N. 1.,. assignors to Radio Corporation of America, a corporation ofDelaware Application June 8, 1946,-Serial No. 675,506

71 Claims. 1

This invention relates to electronic reading aids .for the blind andparticularly to an improved apparatus for concurrently and synchronouslymodulating the frequency I of `the audio tone, which is used to identifythe position of the black areas constituting the letters, While sweepingthe scanning lightacross thepr-inted-line. A further object of thisinvention is to provideT an improved electronic reading aid which iscompletely portable and which requires'no alternating current supply.

In .a copending application, Serial No. 560,472, led .October 26, 1944,now Patent Number 2,451,014, Zworykin and Hillier describe and'claimanelectronic reading aid, known sometimes as an Optophone, inwhich a vibratory member. having a spot-producing slit is driven by analternating current magnetic field to (a) cause 'a spotof` light to scanthe printed line, and (b) Vary the,v frequencyI of the oscillator usedto produce the yvariable beat note which identies the `positionfofthespOt oflight. This system has the .disadvantage thata source of `60cycle alternating current is required. Alsofthe useof a xed `and anangularlyy disposed movable slit for .pro-

ducing a-scanning spot has the disadvantage that theymechanical.movement .must be nearlyas great as the scanning distance,so thatthe end of .the reed vibrates through a considerable angleand thereed must be quite long. It is, therefore, a still further object ofthis invention to `produce a simple, compact and vportable Optophonewhichis free from these disadvantages.

In brief, the improved device utilizes an linterymittent contactvibrator Which is .driven by a small battery. The armature carries apowdered ironV element which is located yin the magnetic field of a coilWhose inductance controls the frequency of oneof two beat oscillators.Lightvis focused on the page by `a small mirror adapted to be vibratedabout anaXis in sucha Way that the light spot scans the page Ain therequired vertical direction. The mirror is driven by a coil coupled tothe vibrator coil and actuated by the pulsating Voltage` developedacross the vibrator. This voltage is, of course, determined by themovement of the vibrator armature, and therefore the frequencymodulation is synchronized with the movement of the light.

The novel features that areconsidered characteristic of thisinvention-are set forth-With particularityV in the appended claims. Theinven tion itself, however, bothas to its organization andmethod ofoperation, aswell as additional objects and .advantages thereof, willbest be understood from the following description when read inconnection with the accompanying drawings, in which;

Figure 1 is a block diagram of the essential components shown:schematically in Figure 2, and

Figure 2 is a schematic diagram oi a device made inaccordancefwith thisinvention.

4Referring `tolig, 1, `a small spot of light is caused to move upranddown-lalonga vertical line which-'crosseathekline oi=printbymeans of a'lamp lcmirrorx:andlens. .The mirror is of Aa polished magneticmaterial, or of glass. In the latter case themirror .should-be mountedon a magnetized plate. `The mirror isso positioned that it can beactedonfby the-magnetic field produced by coil 1.

In synchronismvwith'theamotion ofthe light spot the, .oscillator.portion of an .oscillator-converter `tubeltisfrequency,modulated by avibratorefrequencyzmodulator {Luv/hier; also provides theenergizir-1g;current `for coil l. .The movement lof the mirrorisarranged so that the frequency is high when-the-spot is attthe top ofthe. line and ylow-when the.: spot is..at the bottom of the line. Thelight reflected from the pageis picked up by a Lucite member .'.I3andappliedl to a photoelectric device:y I5; and then to an amplifier Il. Afixed frequency oscillator t9 `.and the amplifier Il lareconnected totheconverter, the former to produce Ian laudio .beat note proportioned tothe difference in. frequency between the two oscillators, andthe latterso yas tooontrol the amplitude of .the output infsuch l,a manner that asignal is producedonlyiw-hen thefspot ison a black area. Thus .thefrequencyof the tone Will depend upon the position and extent -of theblack area beingscanned. Ifthe black-area hastav large verticaldimension, the:y audiol frequency willl vary appreciably during theperiod it is .applied to the ear, giving a Warbledwcharacter tothe;tone, the range yof the frequency variation being a :measure of theVerticalI extent `of thewblack area. As the ylines of letters aremanual-ly ,scanned horizontally along the line,v audibleinformation isthus obtained as to the number, thexsize, and position of black areas,undera the lightatvany. position of the;V instrument. .The variation-otthe sound represent these characteristicsas the letters and .Words arescanned successively.

,Theirequencyof vertical scanning is determined. bythe reading speed.If, forexample, a readingspeed of vsiXty..-vvords per minute islassumed, the letter frequency would be three hundred-per-minute `orfive, per second, on. the

.rate: u :1*

ansiosi) the usual limits of frequency-responseofcQinponents in thesmall sizes necessarilynused:v the instrument described, theupperff'approximately4000 cyclesf" of a letter to be identied suchas theftopbar.v

If the vertical extent of the smallestportion4 l5 o1 an n or m is takenas 15 percent ofthe maximum height of a letter, then the duration yof-fthis sound will be, at the 30 cycle (60 scans) I SGC.

i. Then nthe lowest frequency; .that can bef-used to obtain even onefull cycle per scan will beg-400 With such a sliiort.durationlxtllesoundsglose their tonal character,- atleast A to 12 cycles, beingnecessary torecognize ,asound as aft/one in this f frequency; grange.V-QI'here is,` i however, ai ditin-Ct difference between asound,of%00second durar tionat 400. cyclesandpne-of thesame duration at,esay, 2000cycles; thefnrstbeingfpopularly de,- scribedas` 'a fthump .and` thelatter` taking Von z the character of `a .cliclni` ALongerdurations, asrepresented by the Vertical parts of an ;n, of :course take on a'imoretonal character. .1 The instrument isA preferably. composedzlof 1 twoparts; .the stylus which, is'zh-eld inlthe hand l'and moved along .fthelines,l Vand 1a -smallgcasezzcon- -taining thefv batteries landvlauXiliary apparatus. The elements? shown' -within the" dotted-.line linFig. 2y are preferably contained 4withinrthe stylus.

Av 'miniature dual pre-amplifier tube: is vusedfto f Conserve'space' Yt. l. v The circuit connections'ar'eshown-i Iig. 2. The'- audible.frequencyi is producedfiby. conventional beat-frequency methods."TubefZl isla fixed frequencyoscillatorfwhich iscoupledv to the thirdgridf25 of the convertor-oscillator tube 23.` The-oscillatorfrequency'is off-the lorderl'of 50 kc;V s jT-he vari'ablefrequencyvoscillatorutilizes the vfirst grid `12'! and secondand'lfoiirth'grids;i 29 of tube"23. The frequency-"Contrllingcircitincludes Aa coilV 3 l.. mountedr on* a U -shaped lami nated ironfc'oreil?, Vand tuned to? the 'desired-Y frequencyi by i shuntv capacitors`vr` 35;".-V 3`l.`j Adjacent the open end's of core 3.3|` there is an'r`element of the pole pieces: I e' and hence of the spot of light.

4 energized by a small storage cell 45. The mir ror driving coil 'l isconnected in parallel with the Vibrator through a Variable resistor i9which is used to control the amplitude of Vibration of the mirror. Thispermits easy adjustment of the length of the scanning line. Since theVoltage Aacross thevibrator, ,is determined., by the .lmovlem'entfofthearmature t iff, :the'gf' frequency of thevaria'ble frequencyroscillator' is 'modulated synchronously with the movement of the mirror,The mirror 5I is preferably,;held. .in-normal position by a hairspring53,A vand may be Weighted so that its natural period y"of oscillationwill `coincide with the j'scanningyfrequency, that is, with thefrequency ofthevibrator G3. Lamp 55 is preferably a small aircraftindicator type lamp.

The light reflected from the paper is collected by th'e-Lucite conductori3 vand applied to a photosensitive element-5l, which may be a pho-Ltoresistive l 'or Yphotoenriissivecell;v f .They output of lthiscellamplified vby la I.two-stage hearing aid type tube v59, and vthen by "a"4fur-ther pentodelam- -plier vlil iin the carryingfcase. Theoverallyoltyage gain' is approximatelyv '3000'. The l gainlof the signallevel inthe-connecting 'cable isqniterhigh, preventing any troublefromfmicrophonics, pick'- 'u'pfetcl Batteryl lili supplies f power f 'to-.all tube! `la1 ments, the lamp 55 and Vibratorn l3.-"-Forl mosteconomical operation; this fbattery lislprefer'ably a 10a; 'h'.jstorageicell: fPlate'yoltageis' supplie by "a" 671/2" vfd'ry cell-'ea iThe output circuitv consists of- 'afvolume control potentiometer 65"followed by' *af highpassgJ filter '6l fand -stepdow'n'transformer 59feedingajharing V"aid'type headphone l `l r'lhe purposefof thehigh-'passlter isto r'e'move'any of thef-30cycle moduiating frequencyLremainingin ftnelsi'gn'ai. Grid' 25 efffthe cenverterffosci1iatritubev23ers maintained" at a normally "-negativej@ potential whichissufliciently large'toprevent corren 'flow inthe absence 'of a signal`from"jampliiier ll -A positive' pulse' from 'photocell 'Ei'l appliedjto grid 2 5, through "the 'aInDlieIf, permits l signal vtol reach theoutput"'circi1it "only wherr'the4 ls 'nningspot is "'onja" `blackpart'jof'-the print Y- "what Weeiairn'is? r1 'L'In a'readingaidYhavingfavariable frequency oscillator'and alight' source' for'scanninga'fline 4of 'printed-matter; "the combination fof *an interimittent contact vibrator having* i vibratable 'armaturef-a reactan'ce'elementwhichcontrolsilthe frequency 'of operation :of Jrsaid oscillator;rneans including saidl armature for varying thejrfeactance of 4saidelement "infaccordancewith the movement of- 'said'r armatureVA toythereby` modulate lthe ffre quency'of said oscillator',`v and means'controlled by said vibratorfor movinga bearno'f vlightfrorn saidsourcevso as"to'-'-scan saidfeline-'of printed matter lin'lsyncdnr'onisn1-. vwith the "rnodnl'a 'on' of the frequencycf ysaidfoscillator. 4 l 2. 1n a reading" aid;'the- -conbination'inclur ng fixedfrequency"oscillator-tandati/arial e'v` quenc'y oscillator', said varialeA frequent: f rior-includingarmen@eerdere: t tentcontact'vibrator-having'ainovablea g ture; means includingy saidarmatureffor'y Vyin the reactance-of saidel`e1nent;Y meansff'orproducing aispotof light ;v n i'eansv synchror'iizedy 'Eysaidfvib l torfor moving said 'spot of light''across,anjav means for combiningoscillations prjoducledby said fixed and said I variable frequencyoscillators. to

produce a beat note,Y and vmeans Yfor yaryin'gth' intensity of said beatnote in accordance with the amount of light reflected from the saidarea, whereby the frequency and amplitude of said beat note defines thereflectance of points along said area.

3. A device of the character described in claim 2 in which said meanssynchronized by said vibran tor for moving said spot of light includes amirror and a coil connected to said vibrator for producing a magneticfield which vibrates said mirror.

4. A device of the character described in claim 2 in which saidreactance element comprises a coil the inductance of which is varied bysaid armature.

5. In a reading aid, the combination including a xed frequencyoscillator and a variable frequency oscillator, said variable frequencyoscillator including a reactance element; an intermittent contactvibrator having a movable armature; means including said armature forvarying the reactance of said element; means including a vibratablemirror for focusing a spot of light on a surface to be scanned; meansfor vibrating said mirror in synchronism with said vibrator; means forcombining oscillations produced by said xed and said variable frequencyoscillators to produce a beat note; and means for varying the intensityof said beat note in accordance with the amount of light reflected fromsaid surface, whereby the frequency and amplitude of said beat notedefines the reflectance of points along said surface.

6. In a reading aid, the combination including a fixed frequencyoscillator and a variable frequency oscillator, said variable frequencyoscillator including an lnductor for determining the frequency thereof,an intermittent contact vibrator having a movable armature, meanscarried by said armature and cooperating with said inductor to vary thefrequency of said variable frequency oscillator, means including avibratable mirror for focusing a spot of light on an area to be scanned,a coil associated with said mirror and connected to said vibrator forvibrating said. mirror in synchronism with the movement of saidarmature, means for combining oscillations produced by said xed and saidvariable frequency oscillators to produce a beat note; and means forvarying the intensity of said beat note in accordance with the amount oflight reflected from the said area, whereby the frequency and amplitudeof said beat note defines the reflectance of points along said area.

7. A device of the character described in claim 6 in which said inductoris mounted on a laminated iron core and said armature carries a powderediron element which cooperates with said core to vary the inductance ofsaid inductor.

VLADIMIR K. ZVORYKIN. LESLIE E7. FLORY.

REFERENCES CITED The following references are of record in the le ofthis patent:

UNITED STATES PATENTS Number Name Date 1,320,366 Houskeeper Oct, 28,1919 1,350,954 Stroud et al Aug. 24, 1920 1,352,940 Brown Sept. 14, 19201,848,882 Hausrath et al Mar. 8, 1932 1,873,926 Centeno V. Aug. 23, 1932OTHER REFERENCES Reading Aid for the Blind, by V. K. Zworykin and L. E.Flory, RCA Labts., Radio Corp. of America, Princeton, N. J.

